1、Designation: D7945 16Standard Test Method forDetermination of Dynamic Viscosity and Derived KinematicViscosity of Liquids by Constant Pressure Viscometer1This standard is issued under the fixed designation D7945; the number immediately following the designation indicates the year oforiginal adoption
2、 or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the measurement of dynamicviscosity and density for
3、 the purpose of derivation of kinematicviscosity of petroleum liquids, both transparent and opaque.The kinematic viscosity, , in this test method is derived bydividing the dynamic viscosity, , by the density, , obtained atthe same test temperature. This test method also calculates thetemperature at
4、which petroleum liquids attain a specifiedkinematic viscosity using Practice D341.1.2 The result obtained from this test method is dependentupon the behavior of the sample and is intended for applicationto liquids for which primarily the shear stress and shear rate areproportional (Newtonian flow be
5、havior).1.3 The range of kinematic viscosity covered by this testmethod is from 0.5 mm2/s to 1000 mm2/s in the temperaturerange between 40 C to 120 C; however the precision hasbeen determined only for fuels and oils in the range of 2.06mm2/s to 476 mm2/s at 40 C and 1.09 to 107 mm2/s at 100 C(as sta
6、ted in Section 12 on Precision and Bias). For jet fuels,the precision of kinematic viscosity has been determined in therange of 2.957 mm2/s to 5.805 mm2/s at 20 C and5.505 mm2/s to 13.03 mm2/s at 40 C (as stated in Section 12on Precision and Bias), and the precision of the temperature at12 mm2/s (cS
7、t) has been determined in the range of 38.3 C to58.1 C (as stated in Section 13 on Precision and Bias). Theprecision has only been determined for those materials, viscos-ity ranges, and temperatures as indicated in Section 12 onPrecision and Bias. The test method can be applied to a widerrange of ma
8、terials, viscosity, and temperature. For materialsnot listed in Section 12 on Precision and Bias, the precision andbias may not be applicable.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport
9、 to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D341 P
10、ractice for Viscosity-Temperature Charts for LiquidPetroleum ProductsD445 Test Method for Kinematic Viscosity of Transparentand Opaque Liquids (and Calculation of Dynamic Viscos-ity)D1655 Specification for Aviation Turbine FuelsD2162 Practice for Basic Calibration of Master Viscometersand Viscosity
11、Oil StandardsD6300 Practice for Determination of Precision and BiasData for Use in Test Methods for Petroleum Products andLubricantsD6708 Practice for Statistical Assessment and Improvementof Expected Agreement Between Two Test Methods thatPurport to Measure the Same Property of a MaterialD7566 Spec
12、ification for Aviation Turbine Fuel ContainingSynthesized Hydrocarbons2.2 ISO Standards:3ISO 5725 Accuracy (Trueness and Precision) of Measure-ment Methods and ResultsISO/IEC 17025 General Requirements for the Competenceof Testing and Calibration Laboratories3. Terminology3.1 Definitions:3.1.1 densi
13、ty (), nmass per unit volume.3.1.2 dynamic viscosity (), nthe ratio between the appliedshear stress and rate of shear of a liquid.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.0
14、7 on Flow Properties.Current edition approved June 1, 2016. Published July 2016. Originallypublished in 2014. Last previous edition approved in 2015 as D7945 15. DOI:10.1520/D7945-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.
15、org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.*A Summary of Changes section appears at the end of
16、 this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.2.1 DiscussionIt is sometimes called the coefficient ofdynamic viscosity or, simply, viscosity. Thus, dynamic viscos-ity is a measure of the resistance to flow or to de
17、formation ofa liquid under external shear forces.3.1.2.2 DiscussionThe term dynamic viscosity can also beused in a different context to denote a frequency-dependentquantity in which shear stress and shear rate have a sinusoidaltime dependence.3.1.3 kinematic viscosity (), nthe ratio of the dynamicvi
18、scosity () to the density () of a liquid.3.1.3.1 DiscussionFor gravity flow under a given hydro-static head, the pressure head of a liquid is proportional to itsdensity (). Therefore the kinematic viscosity () is a measureof the resistance to flow of a liquid under gravity.4. Summary of Test Method4
19、.1 A test specimen is introduced into the measuring cells,which are controlled at a specified and known temperature. Themeasuring cells consist of a horizontal capillary tube withoptical sensors and an oscillating U-tube densitometer. Thedynamic viscosity is determined from the flow time of the test
20、specimen along the capillary under a constant pressure ofcompressed air in conjunction with calculations. The density isdetermined by the oscillation frequency of the U-tube inconjunction with calculations. The kinematic viscosity iscalculated by dividing the dynamic viscosity by the density.4.2 Bas
21、ed on the calculations of at least two kinematicviscosities at different temperatures of a test specimen, thetemperature at which the test specimen attains a specifiedkinematic viscosity is calculated and reported according toPractice D341, Annex A1.5. Significance and Use5.1 Many petroleum products
22、 are used as lubricants and thecorrect operation of the equipment depends upon the appropri-ate viscosity of the liquid being used. In addition, the viscosityof many petroleum fuels is important for the estimation ofoptimum storage, handling, and operational conditions. Thus,the accurate determinati
23、on of viscosity is essential to manyproduct specifications.5.2 Density is a fundamental physical property that can beused in conjunction with other properties to characterize boththe light and heavy fractions of petroleum and petroleumproducts and in this test method is used for the calculation from
24、dynamic to kinematic viscosity.6. Apparatus6.1 Constant Pressure Viscometer:4,56.1.1 Viscosity MeasurementThe Constant Pressure vis-cometer uses the Hagen-Poiseuille principle of capillary flowto determine the viscosity. A length of capillary tube isenclosed horizontally in a thermal block maintaine
25、d at aconstant temperature by thermoelectric coolers/heaters. Thetest specimen is driven to flow along the tube by a constant andregulated pressure of compressed air. The transit time of thetest sample as it flows past an array of optical detectors ismeasured. (See Fig. 1.) The dynamic viscosity is
26、proportionalto the measured transit time.6.1.1.1 Pressure ControlA pressure generating and regu-lating device able to maintain an air pressure between 6.89 kPato 68.9 kPa (1 psi to 10 psi) used to drive a test specimen toflow along a capillary tube.6.1.2 Density MeasurementDensity is measured by a s
27、uit-able method so to achieve the precision in kinematic viscosityas stated in the tables in Section 12. A U-shaped oscillatingsample tube with a system for electronic excitation and4The Constant Pressure viscometer is covered by a patent. Interested parties areinvited to submit information regardin
28、g the identification of an alternative to thispatented item to the ASTM International headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee, whichyou may attend.5The sole source of supply of the apparatus known to the committee at this time
29、is PhasePSL, 11168 Hammersmith Gate, Richmond, BC Canada. If you are awareof alternative suppliers, please provide this information to ASTM Internationalheadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.FIG. 1 Visc
30、osity BlockD7945 162frequency counting as described in the manufacturers instruc-tions is suitable. However, for this test method, the purpose ofthe density result is for the calculation from dynamic tokinematic viscosity.6.1.3 Temperature ControlA thermal block surrounds theviscosity measuring cell
31、 so that both are at the same tempera-ture. A thermoelectric heating and cooling system (see Fig. 1)ensures temperature stability of the block to be within60.01 C from the set temperature.6.2 Autosampler, for use in sample introduction process.The autosampler shall be designed to ensure the integrit
32、y of thetest specimen prior to and during the analysis and be equippedto transfer a representative volume of test specimen into themeasuring cells. The autosampler shall transfer the test speci-men from the sample vial to the measuring cells of theapparatus without interfering with the integrity of
33、the testspecimen. The autosampler may have heating capability as ameans to lower the viscosity of the sample for filling themeasuring cells.6.3 Screen, with an aperture of 75 m, to remove particlesfrom samples that may contain them (see 8.2).7. Reagents and Materials7.1 Sample Solvent, completely mi
34、scible with the sample.7.1.1 For samples that are mutually soluble such as jet fuelsand light middle distillate test specimen, the use of the same orsimilar middle distillates as solvent is suitable. If the solventdries up without residues in an applicable time frame, the useof a separate drying sol
35、vent is not required.7.1.2 For more viscous test specimen, an aromatic solventsuch as toluene is suitable.7.2 Drying Solvent, a volatile solvent miscible with thesample solvent (see 7.1).7.2.1 n-Pentane is suitable.7.3 Dry Air, for blowing and drying of the measuring cells.NOTE 1If the measuring cel
36、l temperature is below or near the dewpoint temperature of the ambient air, the use of an appropriate desiccatoris recommended.8. Sampling, Test Specimens, and Test Units8.1 Sampling is defined as all the steps required to obtain analiquot, and to place the sample into the laboratory testcontainer.
37、The laboratory test container shall be of sufficientvolume to mix the sample and obtain a homogeneous samplefor analysis.8.2 Test SpecimenA volume of sample obtained from thelaboratory sample and delivered to the measuring cells. Thetest specimen is obtained as follows:8.2.1 Mix the sample, if requi
38、red, to homogenize at roomtemperature into an open sample vial. If loss of volatilematerial can occur in an open container, then mixing in closedcontainers, or at sub-ambient temperatures is recommended.8.2.2 Deliver the test specimen from a properly mixedlaboratory sample to the measuring cells usi
39、ng an autosampler.For waxy or other samples with a high pour point, beforedelivering the test specimen, heat the laboratory sample to thedesired test temperature, which has to be high enough todissolve the wax crystals.9. Calibration and Verification9.1 Use only a calibrated apparatus as described i
40、n section6.1.1 and as shown in Fig. 1. The calibration shall be checkedas defined by the lab QA procedures using certified referencestandards as described in 9.2. The recommended interval forviscosity and density calibration is once a year as a minimumor when lab QA procedures dictate. For the calib
41、rationprocedure, follow the instructions of the manufacturer of theapparatus.9.2 Certified Viscosity and Density Reference StandardsThese are for use as confirmatory checks on the procedure inthe laboratory. Certified viscosity and density reference stan-dards shall be certified by a laboratory, whi
42、ch has shown tomeet the requirements of ISO/IEC 17025 or a correspondingnational standard by independent assessment. Viscosity stan-dards shall be traceable to master viscometer proceduresdescribed in Test Method D2162. Density standards shall havea certified uncertainty of the density values of 0.0
43、001 g/cm3.The uncertainty of the reference standards shall be stated foreach certified value (k = 2; 95% confidence level). See ISO5725.9.2.1 Use certified reference standards appropriate to thedesired measuring temperatures of viscosity and density mea-surements for both calibration and verificatio
44、n.10. Procedure10.1 Standard Procedure Using an Autosampler:10.1.1 Set the internal temperature control to the desiredmeasuring temperature.10.1.1.1 For jet fuels, it is optional to set the internaltemperature control to more than one desired measuringtemperatures (for example, 20.0 C and 40.0 C). S
45、ee instru-ment operations manual for more details.10.1.2 Set the determinability limits to the values stated inTable 1 for the specific product and test temperature.10.1.2.1 For products not listed in the precision section, it isthe responsibility of the user of this test method to establishreasonab
46、le determinability by a series of tests.10.1.3 Configure the cleaning and drying routines for theautosampler using sample solvent (see 7.1), drying solvent (see7.2) and drying air (see 7.3) for sufficient cleaning efficiency ofthe product being tested.NOTE 2For specific information on proper configu
47、ration, follow themanufacturers instructions.10.1.4 Transfer a minimum of 25 mL of the test specimeninto a sample vial. Cap or cover the vial as necessary.10.1.5 Load sample vial(s) onto vial tray or holder andanalyze the test specimens.10.1.6 Rerun samples which exceed the determinabilitycriteria e
48、stablished for the sample type being analyzed. (SeeTable 1.)10.1.6.1 If the two determined values of kinematic viscositycalculated from the flow time measurements exceed the stateddeterminability figure (see Table 1) for the product, repeat theD7945 163measurements of flow times until the calculated
49、 kinematicviscosity determinations agree with the stated determinability.NOTE 3When a sample is run or when the procedure is repeated, thedynamic viscosity and density are determined in calculating the kinematicviscosity.10.1.7 Press the “Run” or “Start” key. The apparatus mea-sures the transit time of the test specimen through the capillarytube as per 6.1.1 (and Fig. 1) and thereby calculates dynamicviscosity. The density of the test specimen is measured per6.1.2, and the kinematic viscosity is calculated by dividing thedynamic visco
